Furniture drive with a drive unit

ABSTRACT

The invention relates to a furniture drive with a drive unit which comprises an electric motor and a roller that is rotatable about an axis, the roller having a surface for attaching or winding up a flexible force transmission means. According to the invention, the radial distance of the surface changes in the rotational direction of the roller for forming at least one control cam for the force transmission means.

The present invention concerns a furniture drive comprising a drive unit which has an electric motor and a roller which is rotatable about an axis, wherein the roller has a surface for applying or winding up a flexible force transmission means.

Furniture drives with electric motors are already part of the state of the art. Thus for example WO 2007/147180 discloses a pull-in device for a drawer, wherein an electric motor rotates a roller by way of a drive unit and in so doing winds a pulling means on to the roller, whereby the drawer connected to the pulling means is pulled in the closing direction. A disadvantage of furniture drives of the general kind set forth is that the electric motors used can only provide the full torque, as from a certain rotary speed. That leads to problems when starting up and decelerating furniture parts, for example drawers, by means of a furniture drive of the general kind set forth.

The object of the invention is to provide a furniture drive having a simple device with which starting and deceleration of furniture parts moved with the furniture drive is facilitated.

That object is attained by a furniture drive having the features of claim 1.

The measure defined in the characterising portion of claim 1 provides that, by virtue of a variable radial spacing in the direction of rotation of the surface of the roller, on to which a flexible force transmission means is applied or wound, a control cam for the force transmission means. By virtue of that control cam it is possible to targetedly control the necessary torque that the furniture drive must apply by way of the force transmission means for moving the furniture part. If for example the radial spacing of the surface and thus the radial spacing of the control cam is slight, the torque to be applied is also low. In that way the electric motor can more rapidly provide its optimum rotary speed and thus its full torque.

In a particularly preferred embodiment of the invention the roller itself is driven by the electric motor. Due to the above-specified measure a lower torque is initially necessary to move the furniture part, whereby generally the motor power or the size of the motor of the furniture drive can be reduced.

It is particularly advantageous for the control cam to be designed in such a way that, at the beginning of the movement, the radial spacing of the control cam relative to the axis of rotation is kept at a minimum and then slowly increases until it reaches a maximum radial spacing. That measure means that the motor can more quickly reach its optimum rotary speed. In addition it may be advantageous that, in the further configuration of the control cam, by way of which the force transmission means is caused to bear against or is wound on to a surface, the radial spacing relative to the axis of rotation of the roller is kept constant. It can be provided in that respect that the winding length corresponds to the length of the force transmission means, for example a cable or belt.

Particularly advantageous configurations for the control cam are for example spiral control cams, where the rate of increase in the radial spacing is constant, eccentric control cams or the like.

In an embodiment of the invention it can be provided that the rate of increase at which the radial spacing changes in the configuration of the control cam is not constant, in contrast to a spiral control cam. It can be advantageous in that respect that the rate of increase in the radial spacing is particularly great at the beginning of the control cam and then decreases in the further course of the control cam. It can however also be provided that the rate of increase in the radial spacing of the control cam increases in the course of the control cam or however that the radial spacing at the beginning of the control cam has a low rate of increase, then increases more greatly in the further course of the control cam and again has lower rates of increase in a subsequent region of the control cam.

A particularly preferred embodiment of the invention provides that the radial spacing of the control cam in a first region increases from a minimum value to a maximum value and remains constant in a second region following the first region. That complies with the construction of a furniture drive according to the invention, especially as torque control is necessary only at the beginning of a change in motion, that is to say for starting and decelerating the furniture part, while for the major part of the movement the constant torque that is prevailing after the attainment of a certain rotary speed of the electric motor is fully sufficient. In addition such a control cam with a second region involving a constant radial spacing can avoid the roller which is rotatable about an axis becoming too large and no longer being suitable for installation in a furniture carcass.

In a preferred embodiment of the invention that control cam is formed at an end of the roller. It can however also be possible for the control cam to be provided at the peripheral surface of the roller. That is the case in particular when it is provided that the force transmission means is not wound around the roller a plurality of times.

As when starting the movement, when a furniture part to be moved has to be accelerated, major forces are also necessary when decelerating a moving furniture part. It can therefore be provided that at least one second control cam separate from the first is provided on the roller. In that respect it can be provided that the second control cam is of an opposite configuration to the first control cam. That is the case for example when the control cam is provided by the radial spacing of the surface, at which the force transmission means is applied or wound on, decreasing from a maximum value to a minimum value. In that case, during a motion of the furniture part in one direction, the force transmission means can be wound on or applied at a first control cam while it is unwound or removed at a second control cam. In that respect, less torque is necessary initially in the starting procedure by the first control cam while upon deceleration of the furniture part more force is made available by the second control cam, that is to say support in acceleration occurs at the first control cam at the beginning of the motion of the furniture part, that is to say that makes it easier for the electric motor, whereas at the other control cam there is support for deceleration towards the end of the motion of the furniture part, that is to say a damping action is involved. In a motion in the reverse direction, that support in respect of deceleration and acceleration takes place at the respective other control cam.

It may be advantageous in that respect for the two control cams to be provided at the same end or at the opposite ends of the roller. It may be provided that a mutually opposite control cam is provided on both ends of the roller. On the other hand it may also be advantageous to provide the same control cams at both ends, that is to say for example two respective mutually opposite control cams. The advantage of this is that the arrangement of the ends is immaterial, when fitting the roller.

In a further embodiment it is provided that control cams involving different torque configurations are implemented at the two opposite ends. In that case two mutually opposite control cams can be arranged for example at each end. The control cams which are arranged at the two ends can differ in their rate of increase in the radial spacing from the axis of rotation of the roller.

As already mentioned hereinbefore the force transmission means can be implemented by a cable or a belt. It can be provided in that respect that the force transmission means is fixed with at least one end to the roller. It can also be provided that the force transmission means is fixed with two ends to the roller. That is particularly advantageous in the case of two mutually opposite control cams. During start-up the force transmission means is rolled on from its first end and unrolled from its second end.

Further advantageous configurations of the invention are set forth in the appendant claims.

Further advantages and details will be apparent from the Figures and the accompanying specific description. In the Figures:

FIGS. 1 a and 1 b show a furniture carcass according to the invention with furniture drive and a detail view,

FIG. 2 shows an embodiment of a furniture drive according to the invention,

FIG. 3 shows an embodiment of a furniture drive according to the invention with a device for synchronisation of the drive of the two central rails,

FIGS. 4 a and 4 b show a view of embodiments of control cams on a roller, and

FIGS. 5 a through 5 c show a perspective view of an embodiment of a furniture drive according to the invention and separated details thereof.

It will be presupposed that both opening and also closing of the movable furniture part (for example flap of an article of furniture or a drawer) is possible with a furniture drive according to the invention. In the illustrated embodiment that is achieved by a reversible electric motor. FIG. 1 a shows an embodiment of a furniture carcass 1 according to the invention. In this case a drawer is moved open and shut by a furniture drive 2 according to the invention. FIG. 1 b shows a detail view on an enlarged scale of the portion marked by A, illustrating the furniture drive 2 according to the invention.

FIG. 2 shows a view of an embodiment of a furniture drive according to the invention. In this case a roller 5 is driven by an electric motor 3 by way of a drive shaft (not shown) on which a gear 4 is carried. The roller 4 has a surface on which a force transmission means which in this embodiment is provided by a cable line 26 having a first cable end 8 is wound or applied. A first end of the cable 8 is fixed on a first end of the roller 5. Provided on that end of the roller 5 are two control cams 6, 7, each in the form of a spiral. In the embodiment illustrated here the cable 8 is wound on and unwound along the control cam 6. A second end of the cable 9 is fixed to the opposite end. It can be provided here that one or more control cams are also provided at the end that is closer to the electric motor 3. For example the same control cams can be provided on both ends so that it is immaterial how the ends of the roller 5 are arranged on the drive shaft. It can however also be provided that control cams of different configurations are provided at the two ends to embody different torque configurations.

FIG. 3 shows the same embodiment of a furniture drive according to the invention. The electric motor 3 drives a first central rail (not shown here) by way of the cable line 26. The drive of a second central rail (also not shown here) is synchronised by way of a gear 10 and a shaft 11. It can be provided in that respect that a second electric motor is synchronised by that shaft or that a second central rail is driven directly by way of that shaft 11 and possibly further gears and a further flexible force transmission means, for example a further cable line.

FIGS. 4 a and 4 b show embodiments of control cams 6, 7 on the roller 5. In this case FIG. 4 a shows a first end of the roller 5. In this embodiment both cable ends 8, 9 are fixed at that end and are rolled on and off the control cams 6, 7 which are each in the form of a spiral. In this example the cable line 26 is rolled on along the control cam 6 from the cable end 8 in the opening movement, for example of a drawer, whereby a lower torque is required by virtue of the initially smaller radial spacing relative to the axis of rotation 25 of the roller 5. During the rolling-on process that radial spacing increases in order then to reach the maximum value when the electric motor operates at a higher rotary speed. At the same time a second cable end 9 is unrolled at the other control cam 7. In that respect, the transition into the region of the variable radial spacing involves a damping action, in the above-mentioned example therefore damping of the opening movement of the drawer. When the furniture part, for example a drawer, is closed again, the second cable end 9 is rolled on along the control cam 7. In that case the reverse effects occur, that is to say when starting from the open condition of the furniture part, a lower level of torque is required by virtue of the smaller radial spacing relative to the axis of rotation 25 and in the process of the cable end 8 being unrolled on the control cam 6, a damping action is produced, that is to say an opening damping action. FIG. 4 b shows the opposite end of the roller 5. In this case the Figure shows two other spiral control cams 12, 13 which have a lower rate of increase. In that way it is possible to implement a different torque configuration by refitting the roller 5 whereby the ends of the roller 5 are arranged in reversed relationship on the drive shaft.

FIGS. 5 a through 5 c show the perspective view of a furniture drive according to the invention together with a possible embodiment of the fixing thereof. In this case the two cable ends 8, 9 of a cable line 26 are fixed to the central rail 16 by way of two attachment members 17, 18. It can also be provided that the cable line 26 is in the form of an endless cable. As can be seen from the detail view in FIG. 5 b in this case the cable line 26 passes over two direction-changing rollers 14. FIG. 5 c additionally shows two fixing lugs 20, 21 for the carcass rail 15 and the drawer rail 19. The central rail 16 and the drawer rail 19 are connected together in known manner by a positive control system so that a movement of the central rail 16 results in a corresponding movement of the drawer rail 19. The central rail 16 itself is driven by way of the attachment members 17 and 18, by way of which the cable line 26 connects the central rail 6 to the roller 5 by way of the control cams 6, 7.

It will be appreciated that the furniture drive according to the invention is not limited to the embodiments illustrated in the Figures nor is it intended to be restricted thereby. 

1. A furniture drive comprising a drive unit which has an electric motor and a roller which is rotatable about an axis, wherein the roller has a surface for applying or winding up a flexible force transmission means, wherein the radial spacing of said surface changes in the direction of rotation of said roller for forming a control cam for said force transmission means.
 2. A furniture drive as set forth in claim 1 wherein the roller is driven by the electric motor.
 3. A furniture drive as set forth in claim 1 wherein said radial spacing of said control cam increases from a first region of minimum radial spacing to a second region of maximum radial spacing.
 4. A furniture drive as set forth in claim 3 wherein said control cam is of an at least partially spiral configuration.
 5. A furniture drive as set forth in claim 3 wherein the rate of increase at which said radial spacing of said control cam increases changes in the course of said control cam.
 6. A furniture drive as set forth in claim 1 wherein the radial spacing of said control cam increases in a first region from a minimum value to a maximum value and remains substantially constant in a second region following the first region.
 7. A furniture drive as set forth in claim 3 wherein the radial spacing of said control cam increases in a first region from a minimum value to a maximum value and remains substantially constant in a second region following the first region.
 8. A furniture drive as set forth in claim 1 wherein said control cam is provided at a peripheral surface of said roller.
 9. A furniture drive as set forth in claim 1 wherein said control cam is provided at an end of said roller.
 10. A furniture drive as set forth in claim 1 wherein said roller has two separate control cams.
 11. A furniture drive as set forth in claim 10 wherein the radial spacing of said two control cams changes in opposite relationship.
 12. A furniture drive as set forth in claim 10 wherein said two control cams are provided at different ends of said roller.
 13. A furniture drive as set forth in claim 1 wherein a force transmission means is fixed with at least one end to the roller.
 14. A furniture drive as set forth in claim 1 wherein said force transmission means is a cable or a belt.
 15. A drawer extension guide comprising a carcass rail and a drawer rail, at which at least one rail is driven by a furniture drive as set forth in claim
 1. 16. A furniture carcass comprising a drawer extension guide as set forth in claim
 15. 